Date of Award

Fall 8-31-2017

Document Type

Thesis

Degree Name

MS Marine Science

Department

Environmental and Ocean Sciences

Committee Chair

Mary Sue Lowery

Committee Member

Nicholas C. Wegner

Committee Member

Kevin Stuart

Abstract

Physical fitness metrics were used to assess the health and development of California Yellowtail, Seriola dorsalis, in an aquaculture environment during two grow-out experiments. The first experiment sought to evaluate the effects of a common aquaculture deformity (an improperly inflated swim bladder) that has been hypothesized to impact energy allocation, growth, and development. Metrics including metabolic rate, critical swimming speed, feed conversion ratio, and growth rate, were monitored over a 32-week period in three groups of California Yellowtail: wild-caught (“wild”), healthy hatchery-reared (“inflated”), and hatchery-reared with uninflated swim bladders (“uninflated”). At the start of the grow-out period, wild fish had a significantly lower standard metabolic rate (3.08 ± 0.23 mgO2 min-1 kg-1) than both the inflated and uninflated groups (5.60 ± 0.54 and 6.45 ± 0.66 mgO2 min-1 kg-1, respectively), but this difference was not maintained over time. After a 32-week growout, inflated fish had significantly greater mass (758.6 ± 92.7 g vs. 671.1 ± 128.9 g wild, 636.1 ± 80.4 g uninflated) and girth (23.2 ± 1.1 cm vs. 21.6 ± 1.7 cm wild, 21.5 ± 1.2 cm uninflated) than the other two groups, while uninflated fish had significantly shorter BL (36.5 ± 1.9 cm vs. 38.4 ± 2.7 cm wild, 39.6 ± 2.0 cm inflated). However, the wild fish had the most efficient feed conversion (1.41 vs. 1.49 inflated, 2.08 uninflated) and needed 5.8% less feed than the inflated group, and 47.8% less feed than the uninflated group to gain equivalent mass.

In addition to indicating that it wouldn’t be economical to rear yellowtail with uninflated swim bladders due to their poor growth rates and feed conversion ratios, the results of this experiment revealed that there is room for improvement in the fitness of healthy aquaculture-reared yellowtail by potentially lowering their metabolic rate and feed conversion ratios. The subsequent experiment introduced exercise (which is typically lacking in aquaculture) as a means for improvement of fitness in hatchery-reared fish, and aimed to determine if a short duration of exercise could have lasting effects on the fitness of cultured yellowtail. Fish were forced to swim continuously against a flow in custom designed raceways for two, three, or four weeks, following which, metabolic rate, growth rate, and feed conversion were assessed over a 24-week grow-out period. Results showed that the duration of exercise may have an impact on standard metabolic rate immediately following exercise, with the exercised groups showing about a 9-15% reduction in metabolic rate. However, initial metabolic differences were not retained over time. Similarly, growth rates were stimulated by exercise, potentially because their lower standard metabolic rate reflected more efficient resource use and the ability to efficiently gain weight; however, the positive growth response also weakened with time. These results indicate that exercise could play an important role in the development of this species; however, the timing (e.g. yellowtail life stage and duration of exercise) and environmental variables (e.g. temperature and flow speed) likely play important roles in optimizing the response.

Comments

I would like to thank the NOAA Office of Aquaculture for funding this work and Hubbs-SeaWorld Research Institute for donating the fish that made this work possible. Additionally, I’d like to thank the University of San Diego for their financial support.

Available for download on Wednesday, September 11, 2019

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